Inhabitat » The EcoDrain Cuts Water Heater Use by 40%
http://www.inhabitat.com/2009/03/23/the-ecodrain-cuts-water-heater-use-by-40/

A hot shower is relaxing, but is also a huge waste of energy: we heat our water with massive amounts of natural gas, oil or electricity, then transport the heated water to our tubs for a few seconds of sudsing, before washing it down the drain full of raw, wasted heat and energy! What if we could recapture this untapped source of wasted energy by transferring the heat from that shower waste-water to cold incoming water? The EcoDrain, a simple heat exchange unit, does just that, saving water heater use by up to 40%.